Scientists are able to observe these planets from vast distances. You would think with technological capability like this that we would also be able to detect if planets in these zones possess life on them. Trying to understand how or why this is the case.
In: Planetary Science
We are not able to “observe” these planets like you seem to think.
We look at the star the planet orbits and see its sometimes a bit dimmer and we assume that thats caused by a planet in front of the star.
We are far away from looking at a picture of a planet that has even 4 pixels. Like realy far, like we need a telescope nearly a light year away or a lense the size of a planet.
To know that a planet is in this Goldielocks zone means we only have to know its mass and its orbit around the star, you can know that by looking at how often it passes in front of the star already.
So we dont need a HD picture of a planet to know that it could have liquid water and all that.
But to know there is intelligent aliens on that planet would probanly een require us to send a probe there. From recent storues abiut venus we know detecting a gas is not enough to confirm intelignent aliens.
To understand – when we ‘see’ distant planets it’s like being able to look out your window in New York City and see that someone in LA lowered their window shade by 1 foot. Its less that we’re getting high clarity photos of the snowstorms on P3R-118, it’s that we’re seeing tiny changes in the brightness of stars which we’re able to analyze and determine it’s because a planet has passed in front of the star, making it appear dimmer. We’re getting better, but that’s the gist.
What we can do is detect the chemicals present in the atmosphere of some of these planets and those *could* tell us about life, intelligent or otherwise.
For example, any alien looking at Earth from P2C-257 would instantly know there was tons of life on Earth because of the methane. Methane should naturally decay to reach a balance in the atmosphere and earth was WAYYYYYY to much methane so something must be constantly pushing it out 24/7 that is biological, in this case it’s cow farts. Of course cows aren’t “intelligent” in the way you’re hoping for so who knows what we’ll see and learn, but if we saw a planet with Earth level methane we’d be pretty sure we had found some form of extraterrestrial life.
To make a really simple explanation:
if you go outside, you can probably see a rock somewhere in the distance, even though it’s pretty far from you. But can you tell if there are ants on it?
We know rather a lot about stellar physics, so we can look at a distant star and determine fairly accurately how big and bright it is. With this information, we can figure out the range of distances from the star where liquid water would be able to exist on the surface of a planet orbiting the star. This is the “Goldilocks zone” of the star.
However, we do not have anywhere near the capability to see distant planets with any sort of detail. We can often see that a planet is there, and sometimes we’re able to tell how big the planet is and what the atmosphere is like, but unless there’s already an advanced civilization on that planet producing signals, we can’t tell what’s actually going on on the planet’s surface.
There is a big difference between being able to tell if there is a large ball of rock orbiting a star, and whats on said rock. The farther out into the universe you go the less information that gets back to you. Most of our discoveries of distant planets is more like a blip of data in a spreadsheet rather than an actual photo.
Take earth for example, assuming we try to locate our own planet in the distant galaxy. 70% of our surface is just water. Of the remaining 30% of land, greenland and antarctica are just blobs of ice, as is much of northern asia and north america. and very large portions of North American, Asia, Africa, and Australia are desert or mountains that don’t appear green from space. So there’s not a lot of green reflecting off into space to signal plant life, and while we could probably determine to some extent that earth might have water oceans and a thick atmosphere based on how light reflects, determining oxygen(a major sign of life) would be harder, and even farther out, determining that the planet has oceans might not even be possible. This also doesn’t take into account that on an alien plant, photosynthesizing organisms might not be predominantly green. We have lots of red, purple, yellow, and even blue plants on earth, as well as lots of blue, gray, yellow, and orange lichens, and red and yellow is a fairly common color in space at times.
Now as for our structures. Concrete and metal aren’t going to reflect any unusual colors into space and most of our planet’s surface is not covered by man-made structures. And no far off telescope is going to spot any of our satellites or the international space station. Artificial lighting at night would be a different case, but even then our lights are not nearly bright enough to make it very far into space past our solar system. Radio waves we emit go farther, but by the time you reach our closest neighboring star, our radio waves have degraded and faded to the point where our current technology likely wouldn’t be able to discern it from the background radiation in the universe.
We mostly detect these planets indirectly. The star wobbles because it gets pulled around by planet orbiting it or the star goes dimmer in regular intervals when a planet flies between it and the earth.
This is enough to tell us that there is a planet there and how big it is, but not much more.
When we can look at light passing through the atmosphere we might even get some idea what that is made of and even look for stuff that shouldn’t exist in an atmosphere naturally like oxygen, but that would be an extreme case.
None of this is good enough to pick up intelligent life.
Of course if the life was intelligent enough to have radio and television broadcast we could pick those up. And if they were advanced enough to build vast megastructures like dyson swarm we would be able to see that much easier than planets.
If they were a bit more advanced than us and send out colony ships or at least self replicating probes a short while ago in cosmic terms. We wouldn’t even need to look up to find them, they would be here.
No luck so far, so there are probably no technologically advanced aliens out there.
NASA has done several tests to find intelligent life on Sol-3, the planet we live on. Most of them have been unsuccessful, the ones that work have to do with detecting variable radio broadcasts. We can do that from Mars orbit, but not Jupiter orbit (though one Juno result could be read either way).
We have never been close enough to any planet not in the Sol system to detect intelligent life.
Life in general might be inferred from high free oxygen levels in the atmosphere, and we can do that at significant distance, but that’s just microbes.
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